Isotropic porous graphite foam/epoxy composites with outstanding heat dissipation and excellent electromagnetic interference shielding performances

Abstract

In the field of radio frequency chips package, design of isotropic material was a significant challenge to efficiently resolve undesirable electromagnetic radiation and excessive heat accumulation in confined tiny spaces. Here, a brand-new material design concept was proposed and successfully verified through controllable graphitization degree of carbon materials and curvature of twisted graphite sheets during heating and foaming process of asphalt. Concretely, aromatic compounds of the asphalt condensed to form sheet-like macromolecules, which were twisted and oriented along the pore walls. Eventually, these macromolecules were highly graphitized, which expectedly realized the consummate integration of local orientation and macroscopic isotropy. Particularly, a special interlocking epoxy was introduced to prepare epoxy/graphite foam composites (EP-GFs). The EP-GFs (average pore size 0.09 mm) demonstrated an isotropic thermal conductivity up to 118.5 ± 5.8 W·m−1·K−1. Astoundingly, EP-GFs (average pore size 0.244 mm) showed an isotropic electromagnetic interference shielding efficiency (EMI SE), reaching up to 113 dB in 8–12 GHz. Therefore, the EP-GFs completely integrated outstanding thermal conductivity, excellent EMI SE and isotropy macroscopically. Interestingly, the EP-GFs can be cured by Joule heat of low-voltage direct current, and the primary heating region was the contact interface between copper sheets instead of the whole bonded product. This work offered a facile feasible strategy for fabricating isotropic materials to address heat dissipation and electromagnetic pollution of advanced electronic devices in an economical and environmentally friendly manner.